Flush valve

ABSTRACT

A differential pressure valve for operation over a wide range of system pressures, including relatively low domestic water supply pressures. A probe extends upstream to pick up relatively higher pressure to actuate the valve workings. A yieldable restrictor regulates the pressure drop across the workings of the valve to maintain a suitable pressure differential, and a ball-detent type mechanism provides a snap action from open to closed condition so that the valve does not dither. A shoulder laterally deflects the water passed by the valve in a folded pattern known as the &#39;&#39;&#39;&#39;Coanda&#39;&#39;&#39;&#39; effect, which lessens the forces needed to close the valve and protects the actuating member from sand and other deleterious solid material.

Umted States Patent 1151 3,674,237

Heyer et al. 1 July 4, 1972 1 FLUSH VALVE 2,169,452 8/1939 Ricard..251/32 [72] inventors: William T. my", 225 Mohawk Road; 1,034,8268/1912 Payne ..251/43x [22] Filed: Oct. 28, 1970 [21] Appl. No.: 84,789

[52] U.S.Cl ..25l/32,251/43,251/37 [51] Int.Cl ..Fl6k3l/44 [58]FieldofSeal'ch ..251/20, 30, 37,32, 42,43, 251/44, 46, 122

[56] References Cited UNITED STATES PATENTS 901,584 10/1908 Bowman..25l/32X 1,714,591 /1929 Darrow ..251/42 956,158 4/1910 Pasman ..251/431,004,650 /1911 Hilton ..251/32 /5 a M x 1 Dale F. Soukup, 318 MohawkRoad, both of Santa Barbara, Calif. 93105 Primary Examiner-M. CaryNelson Assistant Examiner-David R. Matthews Attorney-Spensley, Horn andLubitz [5 7] ABSTRACT A differential pressure valve for operation over awide range of system pressures, including relatively low domestic watersupply pressures. A probe extends upstream to pick up relatively higherpressure to actuate the valve workings. A yieldable restrictor regulatesthe pressure drop across the workings of the valve to maintain asuitable pressure differential, and a ball-detent type mechanismprovides a snap action from open to closed condition so that the valvedoes not dither. A shoulder laterally deflects the water passed by thevalve in a folded pattern known as the Coanda" effect, which lessens theforces needed to close the valve and protects the actuating member fromsand and other deleterious solid material.

18 Claims, 3 Drawing Figures 53 Z 46 l 5a 43 PATENTEDJUL 4 1972 SHEET IN2 PKTENTEDJUL 4 1972 3.674, 23?

SHEET 2 BF 2 A TTOE/VEYS.

FLUSH VALVE This invention relates to valves which control the flow offluid from a pipe to a point of usage, determining by their action thevolume which is passed.

The prior art is replete with examples of flush valves which areintended to remain open for such a length of time as to pass apre-determined volume of liquid, and then close. Numerous time-delayedvalves are known for this purpose, one class of which is actuated bydifferential pressure between the inlet water supply pressure and alesser pressure, usually that of the atmosphere. This is a preferredclass of valve, and it is not surprising to find a large number ofvalves in this category.

Such valves involve several serious design criteria in order that onedesign can be used in a large number of installations over a widepressure range. Heretofore this type of valve was not practically usefulin systems with large pressure fluctuations, low system pressure, orvery dirty water. The valve of this invention is useful in suchinstallations.

It is an object of this invention to prove a flush valve actuated bydifferential pressure which has a reliable cycle that is appropriatelyrelated to volume passed, which has a sharp cutoff without dithering,which can work over a fluctuating range, and at low pressures, and whichrequires only a minimum force for its actuation.

It is a further object of this invention to provide a valve whichincludes yieldable means which seeks to maintain a suitable actuatingdifferential pressure when the valve is open, and which also provides avaluable siphon-breaking function.

A flush valve according to this invention includes a pistoncylinderactuator responsive to the differential pressure between the systemsupply pressure and atmosphere. This actuator moves within the inletsystem not only a positive seal to open and to close the system, butalso a yieldable restrictor which not only tends to pass liquid, butalso to maintain a suitable pressure differential. It can also act as asuitable siphon-breaker. In addition, the valve includes a pilot memberwhich is inserted into a region of system pressure. As a result, thevalve can operate over a wide range of system pressures.

A still further feature of the invention resides in means for loweringthe forces required to close the valve, and to. shield the actuatingmechanisms from grit, said means comprising a lateral shoulder thatcreates a Coanda effect at the downstream portion of the valve.

The above and other features of this invention will be more fullyunderstood from the following detailed description and the accompanyingdrawings, in which:

FIG. 1 is a side view elevation'in cutaway cross-section of a flushvalve showing the presently preferred embodiment of the presentinvention;

FIG. 2 is a side view elevation in cutaway cross-section as in FIG. 1,but with the valve in a different operational position; and

FIG. 3 is a section view taken at line 33 in FIG. 2.

Referring to the drawings, there is illustrated a flush valve inaccordance with the presently preferred embodiment of the presentinvention. Flush valve 10 includes a main housing 11 having an internalcavity 12 which in turn is in fluid communication with outlet 13.Threads 14 are provided for connecting outlet 13 to a pipe. Body 15 ispositioned within a cavity 12 and includes an annular flange 16 adaptedto bear against a surface of housing 11. O-ring seal 17 provides a fluidseal between the wall of cavity 12 and body 15.

Pilot guide 18 is received within a recess in the upper portion of body15 and includes an internal bore adapted to receive pilot l9. Cavity 20is formed by a recess in housing 15 and is closed at its upper end byflexible seal 21 fastened to pilot l9 and body 15. The lower portion ofcavity 20 is in fluid communication through passage 22 to valve seat 23.Pilot 19 includes a portion of reduced cross-section extending throughcavity 20 and passage 22, and pilot valve element 24 fastened to pilot19 in cylinder 36 is adapted to close against seat 23. Compressionspring 25 is disposed within cavity 20 and urges pilot 19 to itsuppermost position (as shown in the drawings) along axis 26. Passage 80is provided in body 15 and provides fluid communication between outlet13 and cavity 20, thereby establishing cavity 20 as a region of reducedpressure, because it is always connected to exhaust.

Pilot pin 27 includes a portion 28 of reduced diameter which passesthrough pilot l9 and element 24 to expose a lower surface 29 thereofinto cylinder 36. Detent balls 30 carried by pilot 19 are adapted toengage portion 28 of pilot pin 27, and recess 31 on guide 18 is adaptedto receive balls 30 when they are moved laterally outward. Thearrangement forms a ball-detent mechanism to lock pilot 19 so that ittends to assume only two individual positions.

Push button 33 has a lower surface adapted to engage pilot pin 27. Thebutton is biased upwardly along axis 26 by compression spring 34. Bonnet35 is threaded to housing 11 to hold the push button 33 to the body, andto grip flange 16 between the upper surface of housing 11 and a shoulderin bonnet 35.

Body 15 includes an internal cylinder 36 which is in fluid communicationwith seat 23. Piston 37 is reciprocably mounted in cylinder 36. Cup seal38 is part of the piston, and forms the requisite fluid-sealing, slidingfit with the wall of cylinder 36.

Lower housing 39 is rotatably mounted to housing 11 and is fastened toit by means of lock ring 41. An O-ring seal 42 makes a fluid sealbetween housing 11 and housing 39. Housing 39 can therefore be turned inport 40 to provide alignment facility during installation.

Housing 39 includes an internal bore 43 which'is adapted to receive aprobe 44. Probe 44, as shown particularly in FIG. 3, includes guidemeans such as fins 45 which fit loosely inside the wall of bore 43 sothat the probe 44 is retained generally coaxial within the bore. Itoffers no resistance to sliding motion relative to the wall of bore 43.Probe 44 is threaded to a neck 46 on piston 37 and forms an extension ofthe piston. It will be understood that the purpose of fins 45 is toalign probe 44 as the piston reciprocates along axis 26. The free end ofprobe 44 is in constant fluid communication with the supply pressure,upstream from the main valve seat.

A restrictor element 47 is loosely fitted over neck 46, leaving a closebut definite clearance 47a between them. This ele ment isfrusto-conical, and is proportioned to enter bore 43 and a counter bore47b. There is no effort made to make a seal with this element 47.Instead, it is intended to' be freely slidable, being biased toward bore43 by a compression spring 47c. This element does not make contact withprimary seat 48, but passes beyond it in some positions. It does,however, form a variable orifice 47d between its tapered outer surfaceand a restrictor seat 47e at the lower end of the counter bore. It can,in fact, seat on this seat 47c, but this will not close the passagebecause of leakage along the neck. The variable orifice is smallest whenthere is no fluid pressure opposing spring 47c, and largest when thereis a relatively large pressure. Thus, the restrictor element tends tomaintain a given pressure drop across seat 47c, and maintains a largeenough upstream pres sure at the free end of the probe to enable thevalve to operate. Its primary effect is to keep the upstream pressurefrom dropping too low when the valve is open.

Primary seat 48 is formed at the top of housing 39, and is adapted to becontacted by primary seal 48a. The primary seal is carried in a recess48b in the lower face of piston 37. It is shown closing the valve toflow in FIG. 1, and opening it to flow in FIG. 2.

A deflector surface 50 is formed on piston 37 just above the primaryseal. It lies in a plane normal to axis 26, and is intended to give afolding pattern to the flow through the valve. The effect is known asthe Coanda effect, and substantially reduces the axial force necessaryto operate the piston.

Attention is called to an elliptical circumferential deflector surface51 in the wall of the piston, and also to a deflector shoulder 510 onthe bottom end of body 15. Their functions will be more fully describedbelow.

Piston 37 includes a recess portion 52 into which a bleed plug 53 isthreadably fitted to form a partially closed cavity 54.

Metered passage 55 through plug 53 provides fluid communication betweencavity 54 and the internal portion of cylinder 36. Also bore 56 throughneck 46 and metered passage 560 through probe 44 provides fluidcommunication between the inlet and cavity 54. A pin 57, having its head58 in cavity 54 is received in bore 56 and passage 56a to keep the boreand passage clear of debris. The axial position of plug 53 can beadjusted by turning it.

Inlet fitting 60 is fastened to the lower portion of housing 39 byretainer nut 61. An O-ring 62 forms a fluid seal between inlet fitting60 and housing 39. A restrictor valve includes a plug 63 which isthreadably assembled to threaded fastener 64 which in turn is joumaledto housing 39 through passage 65 and held in position by flange 66 andlock ring 67. Fastener 64 is sealed to housing 39 by means of O-ringseal 68. Head 69 of fastener 64 carries a tool engaging surface, such asslot 69a, so that fastener 64 can be rotated. Plug 63 is guided by meansof key 70 which is engaged to a key slot so as to travel along the axisof fastener 64. Plug 63 adapted to close against seat 71 of inletfitting 60 to provide a shut-off valve and, if desired, also aflow-limiting valve.

In operation of the flush valve in accordance with the presentinvention, plug 63 is moved to a position spaced from seat 71 so thatthe plug regulates the volume of fluid flowing from the inlet into bore43. Hence, plug 63 and seat 71 operate as a flow-limiting valve. Asource of pressurized fluid is connected to the flush valve via inletfitting 60 so as to admit pressurized fluid into bore 43 and to impingeupon the lower part of valve element 47. Pressurized fluid also passesthrough metered aperture 56a and bore 56 into cavity 54 within piston37. Also, fluid under pressure passes through metered passage 55 intocylinder 36 above piston 37.

Since the pilot valve associated with valve seat 23 and seal 24 isinitially closed (FIG. 1), the pressure within cylinder 36 is the sameas that in cavity 54, bore 56, and bore 43 below valve element 47.However, cavity 12, being in fluid communication with outlet 13, is atexhaust pressure. Since the crosssection area of piston 37 in cylinder36 is greater than that of the primary seat, and the remaining region ofthe lower face of the piston is exposed to exhaust, the net axial forceon the piston is such as to close the valve and hold it closed.

When the valve is to be opened button 33 is pressed down. It bearsagainst pin 27, and the conical surface on the pin forces the poppetalong by virtue of the engagement between this surface and the balls,and of the balls with the walls of the recesses. Finally, the poppetreaches the position shown in FIG. 2, and the balls are displacedlaterally to hold the poppet locked open.

Cylinder 36 is now bled to exhaust, and a differential force appears toforce the piston upwardly. It is aided by dynamic forces on the lowerside of the piston, but primarily results from the action of spring 470,which is derived from forces applied against restrictor element 47.Element 47 and the piston are in a state of opposition, and, withcylinder 36 vented to exhaust, the net force is upward.

The rate of upward motion is limited by the size of the ventingorifices, and the motion continues until plug 53 strikes the end of pin27 to release the detent lock. Then spring 25 forces the pin upwardlyand seals the vent. The length of the cycle can be adjusted byadjustably positioning plug 53 along the axis so that it closes the ventsooner or later. Then next the cycle continues with the refilling ofcylinder 36 from the pressurized supply. This rate is governed by thesize of orifice 55. Finally, the refilling is completed, and at thistime the primary seal is closed and the valve awaits its next actuation.

A feature of the invention resides in the fact that restrictor element47 rides on a balance of forces provided by bias spring 59 and thepressure at seat 48. When the valve is operated, if the supply pressureis low, the restrictor element will not move as far off the primary seat48 as would occur had the pressure been higher. This occurs because biasspring 59 urges the poppet element against the seat. Also, the biasforce provided by spring 59 is dependent upon the axial position ofpiston 37 and is greatest when the piston is in its retracted, or mostdownwardly position, and is least when the piston is in its uppermostposition. Thus, if the supply pressure is low, piston 37 will moveupwardly when the pilot valve is operated thereby reducing the biasforce provided by spring 59. But instead of merely opening the mainvalve (which could result in substantially diminishing the pressure atthe inlet so the pressure would be insufficient to operate on the pistonin the cylinder-thereby resulting in the valves remaining openindefinitely), restrictor element 47 opens only a small distance fromthe valve seat so that a greater pressure drop is formed at orifice 47d,and the pressure at that point remains high enough to be passed on tocylinder 36 to operate on piston 37 to close the valve.

Since the area of cylinder 36 is substantially greater than the area ofthe bore 43, the resultant force, which is dependent upon the relativereaction surface areas, forces piston 37 toward seat 48, and spring 59holds element 47 seated against seat 48.

Another feature of the invention resides in the fact that the pilotvalve snaps between its open and closed positions. Hence, when the valvecycle is initiated and push button 33 is depressed, pilot pin 27 urgespilot 19 open by virtue of the locking action of balls 30 carried byguide 19. Hence, pilot 19 opens the pilot valve by directed action ofpush button 33. When timing plug 53 contacts surface 29 of pin 27 duringthe closure of the pilot valve, the pin is moved to a position to permitballs to release pilot 19 so that the pilot snaps back to its originalposition. This feature prevents dithering of the valve due to incompleteclosure of the pilot valve, because there is no condition at which theforces on the pilot valve are balanced while it remains open andunlocked.

Still another feature of the invention resides in the fact that probe 44extends into bore 43 so as to be in constant fluid communication withthe supply pressure, and not be substantially affected by any decreasein pressure near valve seat 48. This enables the valve to be used in awide range of supply pressures and flow rates. The metered aperture 47dfurther assures that the upstream pressure is maintained.

Further attention is called to the recessed surface 51. The flow pastthe primary seal is directed sidewardly by surface 50, and this flowthen folds inwardly toward the central axis, except in the regionbounded by port 13. The recessed surface channels sand, debris, and thelike, toward the center of the recess and thereby away from cylinder 36.This protects the cylinder from damage by this debris. Furthermore, thefoldedback flow impinges more heavily on the lower portion of therecessed surface than on the upper while the valve is open and the upperpart is partially shielded. The result is an augmented downward forcewhich assists in the shutting of the valve that is especially usefulwhen low system pressures are involved.

With further regard to this folded pattern, attention is called tosurface 51. For reasons not completely understood, the folded patternappeared to give some troubles near the moment of valve closure. Thisshoulder limits the scope of this pattern, and has eliminated thatproblem.

A further feature of the invention resides in the fact that the upperhousing 11 is joumaled to lower housing 39 so that the inlet and outletportion of the valve may be rotated to any desirable relative position,and not necessarily in the same plane. This takes advantage of the factthat, unlike prior art valves which require substantially verticalinstallation, this valve will run in any position.

The valve according to the present invention may be adjusted for varioustime/volume combinations. For example, if a customer desires a largeflow in a short period of time, plug 53 is adjusted to a relativelyhigh" position near the upper surface of piston 37 so that it willoperate pin 27 before the piston has accomplished its full travel intothe cylinder. Also, the metering valve at the inlet is adjusted so thatelement 63 is unseated from seat 71 as far as possible. Hence, a maximumflow past element 63 is permitted and the plug 53 permits the valve tooperate for a minimum period of time. On the other hand, if the customerdesires a relatively long period of time for the flow but a smallquantity, as in the case of most urinals, the metering valve may beadjusted so that the flow of fluid past seat 71 is maintained at aminimum and plug 53 is adjusted deep into piston 37 so that the timingscrew will not contact pin 27 until the piston has made almost its fulltravel into cylinder 36. The fluid passed by the valve may be regulatedfor any desirable quantity, ordinarily between one-half pint and 5gallons, and the flow may be adjusted for various periods of time inaccordance with the particular use of the valve.

This valve, because of its many features, can be made pn'ncipally of ahard molded plastic material such as Delrin. This results in a largesaving over those which are made entirely of metal. However, it is notpracticable to make plastic parts as large as metal parts for valves ofthis class, and therefore the reduction in size permitted by thedetailed construction is of considerable importance.

This invention is not to be limited by the embodiment shown in thedrawings and described in the description, which is given by way ofexample and not of limitation, but only in accordance with the scope ofthe appended claims.

WHAT IS CLAIMED IS:

1. In a valve of the class having a housing with an internal flowpassage having an inlet and an outlet thereto with a primary seattherein, a piston carrying a primary seal to engage said primary seat, acylinder in which said piston is reciprocable, and valve meanscontrolling the venting of said cylinder to move the piston toward andaway from the primary seal so as to close or to open the valve,respectively, the improvement comprising: a probe carried by said pistonand extending through the primary seat into the flow passage andterminating upstream of the primary seat, there being a passage throughthe probe from the region of termination to the cylinder, an restrictorelement slidably fitted to said probe upstream of said primary seal, anda spring biasing the restrictor element toward the upstream direction,the restrictor element comprising an annular body adapted to make avariable area orifice in said flow passage downstream from the free endof the probe.

2. Apparatus according to claim 1 in which fins are disposed on theprobe to maintain it in alignment.

3. Apparatus according to claim 1 in which a counterbore is formed inthe flow passage upstream from the primary seat with which therestrictor element cooperates to form said variable area orifice.

4. Apparatus according to claim 1 in which a deflector surface is formedadjacent to and surrounding said primary seal to direct fluid laterallyfrom said primary seal.

5. Apparatus according to claim 4 in which a concave peripheral grooveis formed in the outer wall of the piston, the deflector surface beingupstream therefrom and of greater diameter.

6. A valve operable by differential fluid pressure, comprising: ahousing with an internal flow passage having an inlet and an outlet; aprimary seat in said flow passage; a cylinder having a central axis; apiston making a sliding, fluid sealed fit in said cylinder, and axiallyshiftable therein; a primary seal carried by said piston adapted toengage the primary seat and close the flow passage in one axial positionof the piston, and to leave it open in another axial position thereof; aprobe mounted to said piston and passing through the primary seat, andhaving a bore extending from the downstream end of the piston to aportion of the probe upstream from the primary seat in all axialpositions of the piston; a vent passage extending from the cylinder onthe downstream side of the piston to a region of lesser pressure thanthe pressure supplied to the valve; a poppet valve adapted to open or toclose said vent passage, whereby to connect said cylinder to said lesserpressure, or to leave it closed so that the bore conducts supplypressure to said cylinder, thereby shifting said piston to open and toclose the flow passage at the primary seat, respectively;

a position lock to restrain the poppet valve in its open position untilcontacted by the piston; a restrictor element slidably fitted to saidprobe upstream of said primary seal; a spring biasing the restrictorelement toward the upstream direction, the restrictor element comprisingan annular body adapted to make a variable area orifice in said flowpassage downstream from the free end of the probe; an annular deflectorsurface on said piston surrounding and adjacent to said primary seal todirect fluid laterally from said primary seal; and a concave peripheralgroove in the outer wall of the piston of lesser lateral extent than thedeflector surface.

7. A valve according to claim 6 in which the position lock is aball-detent mechanism.

8. A valve according to claim 6 in which an axially adjustable elementis threaded to the piston to adjustably determine the position occupiedby the piston when it contacts the position lock.

9. A valve according to claim 6 in which a counterbore is formed in theflow passage upstream from the primary seat with which the restrictorelement cooperates to form said variable orifice.

10. A valve according to claim 9 in which said restrictor element has atapered outer surface which narrows as it extends in an upstreamdirection.

11. A valve according to claim 10 in which an axially adjustable elementis threaded to the piston to adjustably determine the position occupiedby the piston when it contacts the position lock.

12. A valve according to claim 11 in which the position lock is aball-detent mechanism. t

13. A valve according to claim 12 inwhich a push button is providedadjacent to the poppet valve to abut and open the same when pressed.

14. A valve according to claim 13 in which the housing is formed of twoparts which are rotationally joined to each other, the outlet beingformed in one of said parts and opening into the housing laterallyrelative to the axis of the cylinder.

15. A valve according to claim 14 in which the cylinder is formed withina neck in said housing, said neck extending axially into a cavity intowhich the outlet opens, there being a second deflector surface at theupstream end of said neck.

16. A valve according to claim 15 in which a restrictor valve isdisposed upstream of the probe to limit flow through the valve.

17. A valve according to claim 15 in which fins are disposed on theprobe to maintain it in alignment.

18. In a valve of the class having a housing with an internal flowpassage having an inlet and an outlet thereto, with a primary seattherein, a piston carrying a primary seal to engage said primary seat, acylinder in which said piston is reciprocable, the piston being movabletoward and away from the primary seat to close or to open the valve,respectively, the improvement comprising: an axially shiftable poppetvalve so disposed and arranged as to open or to close thereby to ventthe cylinder or to close it, and a position lock having a ball-detentmechanism adapted to restrain the poppet valve in its open positionuntil contacted by the piston.

1. In a valve of the class having a housing with an internal flowpassage having an inlet and an outlet thereto with a primary seattherein, a piston carrying a primary seal to engage said primary seat, acylinder in which said piston is reciprocable, and valve meanscontrolling the venting of said cylinder to move the piston toward andaway from the primary seal so as to close or to open the valve,respectively, the improvement comprising: a probe carried by said pistonand extending through the primary seat into the flow passage andterminating upstream of the primary seat, there being a passage throughthe probe from the region of termination to the cylinder, an restrictorelement slidably fitted to said probe upstream of said primary seal, anda spring biasing the restrictor element toward the upstream direction,the restrictor element comprising an annular body adapted to make avariable area orifice in said flow passage downstream from the free endof the probe.
 2. Apparatus according to claim 1 in which fins aredisposed on the probe to maintain it in alignment.
 3. Apparatusaccording to claim 1 in which a counterbore is formed in the flowpassage upstream from the primary seat with which the restrictor elementcooperates to form said variable area orifice.
 4. Apparatus according toclaim 1 in which a deflector surface is formed adjacent to andsurrounding said primary seal to direct fluid laterally from saidprimary seal.
 5. Apparatus according to claim 4 in which a concaveperipheral groove is formed in the outer wall of the piston, thedeflector surface being upstream therefrom and of greater diameter.
 6. Avalve operable by differential fluid pressure, comprising: a housingwith an internal flow passage having an inlet and an outlet; a primaryseat in said flow passage; a cylinder having a central axis; a pistonmaking a sliding, fluid sealed fit in said cylinder, and axiallyshiftable therein; a primary seal carried by said piston adapted toengage the primary seat and close the flow passage in one axial positionof the piston, and to leave it open in another axial position thereof; aprobe mounted to said piston and passing through the primary seat, andhaving a bore extending from the downstream end of the piston to aportion of the probe upstream from the primary seat in all axialpositions of the piston; a vent passage extending from the cylinder onthe downstream side of the piston to a region of lesser pressure thanthe pressure supplied to the valve; a poppet valve adapted to open or toclose said vent passage, whereby to connect said cylinder to said lesserpressure, or to leave it closed so that the bore conducts supplypressure to said cylinder, thereby shifting said piston to open and toclose the flow passage at the primary seat, respectively; a positionlock to restrain the poppet valve in its open position until contactedby the piston; a restrictor element slidably fitted to said probeupstream of said primary seal; a spring biasing the restrictor elementtoward the upstream direction, the restrictor element comprising anannular body adapted to make a variable area orifice in said flowpassage downstream from the free end of the probe; an annular deflectorsurface on said piston surrounding and adjacent to said primary seal todirect fluid laterally from said primary seal; and a concave peripheralgroove in the outer wall of the piston of lesser lateral extent than thedeflector surface.
 7. A valve according to claim 6 in which the positionlock is a ball-detent mechanism.
 8. A valve according to claim 6 inwhich an axially adjustable element is threaded to the piston toadjustably determine the position occupied by the piston when itcontacts the position lock.
 9. A valve according to claim 6 in which acounterbore is formed in the flow passage upstream from the primary seatwith which the restrictor element cooperates to form said variableorifice.
 10. A valve according to claim 9 in which said restrictorelement has a tapered outer surface which narrows as it extends in anupstream direction.
 11. A valve according to claim 10 in which anaxially adjustable element is threaded to the piston to adjustablydetermine the position occupied by the piston when it contacts theposition lock.
 12. A valve according to claim 11 in which the positionlock is a ball-detent mechanism.
 13. A valve according to claim 12 inwhich a push button is provided adjacent to the poppet valve to abut andopen the same when pressed.
 14. A valve according to claim 13 in whichthe housing is formed of two parts which are rotationally joined to eachother, the outlet being formed in one of said parts and opening into thehousing laterally relative to the axis of the cylinder.
 15. A valveaccording to claim 14 in which the cylinder is formed within a neck insaid housing, said neck extending axially into a cavity into which theoutlet opens, there being a second deflector surface at the upstream endof said neck.
 16. A valve according to claim 15 in which a restrictorvalve is disposed upstream of the probe to limit flow through the valve.17. A valve according to claim 15 in which fins are disposed on theprobe to maintain it in alignment.
 18. In a valve of the class having ahousing with an internal flow passage having an inlet and an outletthereto, with a primary seat therein, a piston carrying a primary sealto engage said primary seat, a cylinder in which said piston isreciprocable, the piston being movable toward and away from the primaryseat to close or to open the valve, respectively, the improvementcomprising: an axially shiftable poppet valve so disposed and arrangedas to open or to close thereby to vent the cylinder or to close it, anda position lock having a ball-detent mechanism adapted to restrain thepoppet valve in its open position until contacted by the piston.